The investigation will concern itself with the physiology and dynamics of myometrial activity and their relationship to the onset of labor and the distribution of the uteroplacental circulation in monkeys. Specific attention will be directed toward: a) the interrelationships of steroid hormones, prostaglandins, adrenergic receptors, and the adenylate cyclase system in modulation of the demonstrated biorhythms of uterine spontaneous activity and hemodynamics; and b) the role of these agents on the distribution of uterine blood flow to placental and nonplacental sites. Sensors will monitor intrauterine pressure, arterial and venous blood pressures, and blood flow in chronic experimental preparations. Radioisotopes and other indicators will be used to analyze various aspects of placental and nonplacental uterine blood flow. Electronic integration and computer analysis of measured parameters will facilitate evaluation of the studies in an effort to identify and assess some of the factors that control uterine activity and the mechanisms of fetal and maternal uterine homeostasis. A primate breeding colony will be maintained.